This invention relates to derivatives of macromolecules, including polysaccharide derivatives, having increased hydrophobicity as compared to the unmodified macromolecules or polysaccharides. More particularly, the invention relates to oral delivery and absorption of hydrophobized macromolecules and amphiphilic polysaccharide derivatives, such as amphiphilic heparin derivatives, wherein the bioactivity of the macromolecule or polysaccharide is preserved. In preferred embodiments of the invention, the hydrophobized macromolecules and amphiphilic polysaccharide derivatives have a molecular weight of greater than 1000, yet are absorbed after oral administration.
Heparin is a polysaccharide composed of sulfated D-glucosamine and D-glucuronic acid residues. Due to its numerous ionizable sulfate groups, heparin possesses a strong electronegative charge. It is also a relatively strong acid that readily forms water-soluble salts, e.g. heparin sodium. It is found in mast cells and can be extracted from many body organs, particularly those with abundant mast cells. The liver and lungs are especially rich in heparin. The circulating blood contains no heparin except after profound disruption of mast cells. Heparin has many physiological roles, such as blood anticoagulation, inhibition of smooth muscle cell proliferation, and others. In particular, heparin is a potent anticoagulant agent that interacts strongly with antithrombin III (ATIII) to prevent the formation of fibrin clots. Heparin is one of the most potent anticoagulants used for treatment and prevention of deep vein thrombosis and pulmonary embolism. In vivo, however, applications of heparin are very limited. Because of its hydrophilicity and high negative charge, heparin is not absorbed efficiently from the GI tract, nasal or buccal mucosal layers, and the like. Therefore, the only routes of administration used clinically are intravenous and subcutaneous injections. Moreover, since heparin is soluble in relatively few solvents, it is hard to use for coating surfaces of medical devices or in delivery systems.
To improve the properties of heparin, R. J. Linhardt et al., 83 J. Pharm. Sci. 1034-1039 (1994), coupled lauryl (C12) and stearyl (C18) groups to single heparin chains, resulting in a derivatized heparin having increased hydrophobicity but with low anticoagulation activity. This result demonstrated that coupling a small linear aliphatic chain to heparin was ineffective in enhancing the hydrophobicity of heparin while preserving activity. Thus, known heparin derivatives have been ineffective in preserving anticoagulation activity.
T. M. Rivera et al., Oral Delivery of Heparin in Combination with Sodium N-[8-(2-Hydroxybenzolyl)amino]caprylate: Pharmacological Considerations, 14 Pharm. Res. 1830-1834 (1997), disclosed the possibility of oral delivery of heparin using heparin mixed with sodium N-[8-(2-hydroxybenzolyl)amino]caprylate. M. Dryjski et al., Investigations on Plasma Activity of Low Molecular Weight Heparin after Intravenous and Oral Administrations, 28 Br. J. Clin.
Pharma. 188-192 (1989), described the possibility of oral absorption of low molecular weight heparin using enhancers.
It is generally recognized that molecules having a molecular weight greater than 1000 are poorly absorbed in the gastrointestinal (GI) tract after oral administration. For example, J. G. Russell-Jones, Carrier-mediated Transport, Oral Drug Delivery, in 1 Encyclopedia of Controlled Drug Delivery 173, 175 (Edith Mathiowitz ed. 1999), stated that the work of W. Kramer et al., 269 J. Biol. Chem. 10621-10627 (1994), suggested that the maximal size of a peptide that could be transported via the bile acid transporter was four amino acids, or about 600 Da. As another example, P. W. Swaan et al., Enhanced Transepithelial Transport of Peptides by Conjugation to Cholic Acid, 8 Bioconjugate Chemistry 520-525 (1997), reported that bile acid conjugates with up to 6 amino acids (i.e., about 900 Da) showed affinity for the intestinal bile acid transporter, but the only 6-amino-acid bile acid conjugate tested was not transported by the bile acid carrier.
In view of the foregoing, it will be appreciated that development of a method for obtaining absorption of macromolecules having a molecular weight greater than 1000 after oral administration would be a significant advancement in the art. It will also be appreciated that development of a method for obtaining absorption of hydrophobized or amphiphilic heparin derivatives after oral administration would be another significant advancement in the art.
It is an object of the present invention to provide a method for obtaining absorption of molecules having a molecular weight greater than 1000 after oral administration.
It is also an object of the invention to provide a method for obtaining blood anticoagulation by oral administration of amphiphilic heparin derivatives.
It is still another object of the invention to provide heparin derivatives that can be absorbed from the GI tract, thereby facilitating oral delivery for preventing blood coagulation.
It is yet another object of the invention to provide heparin derivatives comprising heparin coupled with a bile acid, such as deoxycholic acid or glycocholic acid, or a hydrophobic agent, such as cholesterol, or an alkanoic acid.
These and other objects can be addressed by providing a method of treating a patient in need of anticoagulation therapy comprising orally administering an effective amount of a composition comprising heparin covalently bonded to a hydrophobic agent selected from the group consisting of bile acids, sterols, and alkanoic acids, and mixtures thereof. The composition can also include a pharmaceutically acceptable carrier.
In one preferred embodiment of the invention the hydrophobic agent is a bile acid selected from the group consisting of cholic acid, deoxycholic acid, chenodeoxycholic acid, lithocholic acid, ursocholic acid, ursodeoxycholic acid, isoursodeoxycholic acid, lagodeoxycholic acid, glycocholic acid, taurocholic acid, glycodeoxycholic acid, glycochenodeoxycholic acid, dehydrocholic acid, hyocholic acid, hyodeoxycholic acid, and mixtures thereof, and the like.
In another preferred embodiment of the invention, the hydrophobic agent is a sterol selected from the group consisting of cholestanol, coprostanol, cholesterol, epicholesterol, ergosterol, ergocalciferol, and mixtures thereof, and the like.
In still another preferred embodiment of the invention, the hydrophobic agent is an alkanoic acid comprising about 4 to 20 carbon atoms. Preferred alkanoic acids include butyric acid, valeric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and mixtures thereof, and the like.
Preferably, the heparin comprises a molecular weight of at least about 3000, and more preferably at least about 6000. In certain preferred embodiments, the heparin comprises a molecular weight less than about 12,000.
Another preferred embodiment of the invention comprises a method for enhancing oral administration of a macromolecular agent comprising:
(a) conjugating the macromolecular agent to a hydrophobic agent selected from the group consisting of bile acids, sterols, alkanoic acids, and mixtures thereof, and the like to result in a hydrophobized macromolecular agent; and
(b) orally administering an effective amount of the hydrophobized macromolecular agent to a patient in need thereof.
Preferably, the macromolecular agent is a member selected from the group consisting of heparin, heparan sulfate, sulfonyl polysaccharide, heparinoids, polysaccharide derivatives, and mixtures thereof, and the like. In another preferred embodiment of the invention, the macromolecular agent is a peptide, such as insulin or calcitonin.